Is it actually waterproof? Simba - Odyssey September 27, 2017 10:59 Follow We've done our research and can confirm they are 100% waterproof - creating the perfect barrier from spills and stains. Related articles Is the protector hypoallergenic? Why should I choose a Simba Mattress Protector? How do I use my Simba Mattress Protector? What is the protector made of? Can you take away my old mattress?